4D‐Printing of Photoswitchable Actuators Lu, Xili; Ambulo, Cedric P.; Wang, Suitu ...
Angewandte Chemie International Edition,
March 1, 2021, Letnik:
60, Številka:
10
Journal Article
Recenzirano
Shape‐switching behavior, where a transient stimulus induces an indefinitely stable deformation that can be recovered on exposure to another transient stimulus, is critical to building smart ...structures from responsive polymers as continue power is not needed to maintain deformations. Herein, we 4D‐print shape‐switching liquid crystalline elastomers (LCEs) functionalized with supramolecular crosslinks, dynamic covalent crosslinks, and azobenzene. The salient property of shape‐switching LCEs is that light induces long‐lived, deformation that can be recovered on‐demand by heating. UV‐light isomerizes azobenzene from trans to cis, and temporarily breaks the supramolecular crosslinks, resulting in a programmed deformation. After UV, the shape‐switching LCEs fix more than 90 % of the deformation over 3 days by the reformed supramolecular crosslinks. Using the shape‐switching properties, we print Braille‐like actuators that can be photoswitched to display different letters. This new class of photoswitchable actuators may impact applications such as deployable devices where continuous application of power is impractical.
Shape‐switching liquid crystal elastomers are formulated where light is used to trigger a shape change which is then stable indefinitely. The original shape can be recovered on heating. These materials can be 4D printed into reconfigurable Braille‐like actuators capable of displaying letters “L”, “C” and “E” by switching the shape‐morphing of the Archimedean chord patterns with UV light and heating.
The persistence of intergroup conflicts around the world creates urgency for research on child development in such settings. Complementing what we know about internalizing and externalizing ...developmental outcomes, in this article, I shift the focus to children’s prosocial behaviors and more specifically, the Developmental Peacebuilding Model (DPM). The DPM makes three main contributions: It (a) integrates a developmental intergroup framework and socioecological perspective with a peace‐building paradigm to examine the target and type of children’s prosocial behavior in settings of intergroup conflict; (b) outlines how children’s outgroup prosocial behaviors, which promote constructive change at different levels of social ecology, can be understood as peace building and fostering social cohesion; and (c) has implications for research and global policy.
4D Printing of Engineered Living Materials Rivera‐Tarazona, Laura K.; Shukla, Tarjani; Singh, Kanwar Abhay ...
Advanced functional materials,
01/2022, Letnik:
32, Številka:
4
Journal Article
Recenzirano
Herein, a method that uses direct‐ink‐write printing to fabricate engineering living materials (ELMs) that respond by undergoing a programmed shape change in response to specific molecules is ...reported. Stimuli‐responsiveness is imparted to ELMs by integrating genetically engineered yeast that only proliferate in the presence of specific biomolecules. This proliferation, in turn, leads to a shape change in the ELM in response to that biomolecule. These ELMs are fabricated by coprinting bioinks that contain multiple yeast strains. Locally, cellular proliferation leads to controllable shape change of the material resulting in up to a 370% increase in volume. Globally, the printed 3D structures contain regions of material that increase in volume and regions that do not under a given set of conditions, leading to programmable changes in form in response to target amino acids and nucleotides. Finally, this printing method is applied to design a reservoir‐based drug delivery system for the on‐demand delivery of a model drug in response to a specific biomolecule.
Direct‐ink‐write printing of engineered living materials facilitates the spatial control of yeast strain and quantity within synthetic hydrogels. Printed materials morph into programmed forms in response to engineered conditions dictated by genetics of the yeast. Using this programmed shape change, drug reservoirs made from these composites are shown to release encapsulated materials in response to specific biochemical cues.
Stimuli-responsive materials are able to undergo controllable changes in materials properties in response to external cues. Increasing efforts have been directed towards building materials that mimic ...the responsive nature of biological systems. Nevertheless, limitations remain surrounding the way these synthetic materials interact and respond to their environment. In particular, it is difficult to synthesize synthetic materials that respond with specificity to poorly differentiated (bio)chemical and weak physical stimuli. The emerging area of engineered living materials (ELMs) includes composites that combine living cells and synthetic materials. ELMs have yielded promising advances in the creation of stimuli-responsive materials that respond with diverse outputs in response to a broad array of biochemical and physical stimuli. This review describes advances made in the genetic engineering of the living component and the processing-property relationships of stimuli-responsive ELMs. Finally, the implementation of stimuli-responsive ELMs as environmental sensors, biomedical sensors, drug delivery vehicles, and soft robots is discussed.
Engineered living materials integrate genetic engineering and synthetic materials to program stimuli responses that enable the fabrication of devices for diverse applications.
Wearable and mobile devices that capture multimodal data have the potential to identify risk factors for high stress and poor mental health and to provide information to improve health and ...well-being.
We developed new tools that provide objective physiological and behavioral measures using wearable sensors and mobile phones, together with methods that improve their data integrity. The aim of this study was to examine, using machine learning, how accurately these measures could identify conditions of self-reported high stress and poor mental health and which of the underlying modalities and measures were most accurate in identifying those conditions.
We designed and conducted the 1-month SNAPSHOT study that investigated how daily behaviors and social networks influence self-reported stress, mood, and other health or well-being-related factors. We collected over 145,000 hours of data from 201 college students (age: 18-25 years, male:female=1.8:1) at one university, all recruited within self-identified social groups. Each student filled out standardized pre- and postquestionnaires on stress and mental health; during the month, each student completed twice-daily electronic diaries (e-diaries), wore two wrist-based sensors that recorded continuous physical activity and autonomic physiology, and installed an app on their mobile phone that recorded phone usage and geolocation patterns. We developed tools to make data collection more efficient, including data-check systems for sensor and mobile phone data and an e-diary administrative module for study investigators to locate possible errors in the e-diaries and communicate with participants to correct their entries promptly, which reduced the time taken to clean e-diary data by 69%. We constructed features and applied machine learning to the multimodal data to identify factors associated with self-reported poststudy stress and mental health, including behaviors that can be possibly modified by the individual to improve these measures.
We identified the physiological sensor, phone, mobility, and modifiable behavior features that were best predictors for stress and mental health classification. In general, wearable sensor features showed better classification performance than mobile phone or modifiable behavior features. Wearable sensor features, including skin conductance and temperature, reached 78.3% (148/189) accuracy for classifying students into high or low stress groups and 87% (41/47) accuracy for classifying high or low mental health groups. Modifiable behavior features, including number of naps, studying duration, calls, mobility patterns, and phone-screen-on time, reached 73.5% (139/189) accuracy for stress classification and 79% (37/47) accuracy for mental health classification.
New semiautomated tools improved the efficiency of long-term ambulatory data collection from wearable and mobile devices. Applying machine learning to the resulting data revealed a set of both objective features and modifiable behavioral features that could classify self-reported high or low stress and mental health groups in a college student population better than previous studies and showed new insights into digital phenotyping.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The growth of multicellular organisms is a process akin to additive manufacturing where cellular proliferation and mechanical boundary conditions, among other factors, drive morphogenesis. Engineers ...have limited ability to engineer morphogenesis to manufacture goods or to reconfigure materials comprised of biomass. Herein, a method that uses biological processes to grow and regrow magnetic engineered living materials (mELMs) into desired geometries is reported. These composites contain Saccharomyces cerevisiae and magnetic particles within a hydrogel matrix. The reconfigurable manufacturing process relies on the growth of living cells, magnetic forces, and elastic recovery of the hydrogel. The mELM then adopts a form in an external magnetic field. Yeast within the material proliferates, resulting in 259 ± 14% volume expansion. Yeast proliferation fixes the magnetic deformation, even when the magnetic field is removed. The shape fixity can be up to 99.3 ± 0.3%. The grown mELM can recover up to 73.9 ± 1.9% of the original form by removing yeast cell walls. The directed growth and recovery process can be repeated at least five times. This work enables ELMs to be processed and reprocessed into user‐defined geometries without external material deposition.
Engineered living materials made from hydrogels with living yeast and magnetic particles can grow repeatedly into user‐defined geometries. This process relies on the growth of living cells, magnetic forces, and elastic recovery of the hydrogel. This manufacturing strategy combining mechanical confinements and biological growth contributes to a future where objects are grown and not merely processed.
Over half of refugees are school‐aged children. In host communities, children's attitudes and behaviours are important for the integration of refugee children. This study examines the ...empathy–attitudes–action model in middle childhood (N = 94, 8 to 11 years old). In both the experimental and control conditions, children were introduced to a (fictional) refugee and told that he or she would be moving to their school. The experimental condition also listened to a storybook about the child's refugee experience. Empathy, outgroup attitudes, and prosocial behaviour toward the incoming child, and refugees as a group, were measured. Although mediation was not supported, the storybook condition reported more empathy and helping intentions, and attitudes predicted helping intentions but not giving to refugees. Results highlight how host‐society children can welcome refugees.
This article examines the role of empathy for outgroup helping, collective action and political activism among youth in Northern Ireland, a setting of protracted conflict. Integrating the ...Empathy-Attitudes-Action model with the Developmental Peacebuilding Model, a two-wave study was conducted to assess youth’s behavioural intentions and actual behaviours toward refugees. Across two waves (N = 383, 52 % male, 48 % female; 14−16 years old), empathy at Time 1 predicted more positive attitudes toward ethnic minorities at Time 2, which in turn was positively related to four outcomes aiming to foster prosocial change for refugees: helping behaviour and realistic helping at the interpersonal level, collective action intentions at the structural level, and signing a petition aiming for cultural change. That is, outgroup attitudes mediated the link from empathy to three types of prosocial action toward refugees. The findings suggest that youth not only volunteer to help an individual outgroup member, but also support broader structural and cultural change that will benefit those they may never meet. Implications for recognising and supporting the constructive agency of youth toward disadvantaged groups in conflict settings are discussed.
Cracks are typically associated with the failure of materials. However, cracks can also be used to create periodic patterns on the surfaces of materials, as observed in the skin of crocodiles and ...elephants. In synthetic materials, surface patterns are critical to micro‐ and nanoscale fabrication processes. Here, a strategy is presented that enables freely programmable patterns of cracks on the surface of a polymer and then uses these cracks to pattern other materials. Cracks form during deposition of a thin film metal on a liquid crystal polymer network (LCN) and follow the spatially patterned molecular order of the polymer. These patterned sub‐micrometer scale cracks have an order parameter of 0.98 ± 0.02 and form readily over centimeter‐scale areas on the flexible substrates. The patterning of the LCN enables cracks that turn corners, spiral azimuthally, or radiate from a point. Conductive inks can be filled into these oriented cracks, resulting in flexible, anisotropic, and transparent conductors. This materials‐based processing approach to patterning cracks enables unprecedented control of the orientation, length, width, and depth of the cracks without costly lithography methods. This approach promises new architectures of electronics, sensors, fluidics, optics, and other devices with micro‐ and nanoscale features.
Cracks are normally classified as material failures to be prevented. A crack patterning strategy is described that allows freely programmable patterns of cracks guided by the alignment of liquid crystal polymer networks. This programmable cracking enables high‐resolution patterning in a high‐throughput manner without the use of expensive lithography procedures and may serve as an alternative fabrication strategy for various applications.
In adolescence, youth spend a high proportion of their time with their peers and in school; it is hardly surprising therefore that perceptions of peer and school norms have a strong influence on ...their attitudes and behaviours. These norms, however, do not always influence youth in the same way. Building on past research, the present study examines the role of peer norms and school norms in influencing the quantity and quality of intergroup contact, as well as the impact of such contact on positive and negative intergroup behaviours. Youth (aged 14–16) living in Northern Ireland (N = 466, evenly split by religion and gender) were recruited through their school as part of a two‐wave study and completed a series of survey measures including intergroup contact (quality and quantity), norms (peer and school), and participation in sectarian antisocial behaviour and outgroup prosocial behaviour. Mediation analysis was conducted in Mplus. Controlling for wave 1 responses on contact and behavioural outcomes, findings demonstrate that more positive peer norms are associated with less participation in antisocial behaviour and more participation in prosocial outgroup behaviours through increased and better quality intergroup contact. Positive school norms were also associated with increased prosocial behaviour, but only though better quality contact. Findings demonstrate the relative importance of peer norms compared to school norms for this age group. The results have implications for school‐based interventions that aim to improve intergroup relations and highlight the importance of peer networks to promote more positive outgroup behaviours in divided societies such as Northern Ireland.
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